Knife sharpener

ABSTRACT

A knife sharpener is made up of a housing containing a sanding belt and a driving system that engages the belt to cause it to move in a sharpening area where a knife can come into contact with the sanding belt. The knife sharpener also includes a first angle guide having a surface against which a first side of a knife can be positioned so the edge of the knife can be positioned in the sharpening area, a second angle guide having a surface against which a second side of the knife can be positioned so the edge of the knife can be positioning in the sharpening area, and an angle adjustment mechanism that can adjust the angle of the first angle guide and the second angle guide to change the angle of the surfaces relative to the sanding belt.

PRIORITY

The present application claims the benefit of domestic priority based on U.S. Provisional Patent Application 62/678,198 filed on May 30, 2018, the entirety of which is incorporated herein by reference.

BACKGROUND

As Washington Irving said, “a sharp tongue is the only edge-tool that grows keener with constant use.” For everything else, a good sharpener is needed. The art of knife sharpening has been honed throughout the ages. From the ancient days of the samurai warriors to the modern days of the iron chefs, a knife wielder is only as effective as the sharpness of his or her blade.

The ease and convenience of knife sharpening has become of paramount importance in today's world. Users no longer want to sit in front of a grinding stone, use a manual knife sharpener, or pay the expense of sending out their knives to have them professionally sharpened. Gadgets and machines have been developed to make the process as simple and effective as possible for cooks and tool users. One such type of sharpener uses a moving sanding belt that can be used to grind the edge of a knife.

However, the belt sharpeners currently available all suffer from one or more drawbacks. For example, current belt sharpeners are designed to only allow for easy and/or consistent grinding of one side of the edge of a knife. In addition, the belt sharpeners do not allow a user to precisely select the angle of grinding over a wide range of angles. Furthermore, conventional belt sharpeners are not able to accurately and consistently grind at a desired angle due to the flexibility of the belt. Moreover, belt sharpeners generate dust and debris that can create a hazardous and/or unclean environment near the sharpener.

There is therefore a need for an improved knife sharpener. There is further a need for a knife sharpener that can easily and consistently grind both sides of the edge of a knife. There is still a further need for a knife sharpener that can precisely select and/or monitor the angle of grind over a wide range of angles. There is still further a need for a knife sharpener that can lessen the inaccuracy and/or inconsistency of angle grinds that result from the flexibility of a sanding belt. There is still further a need for a knife sharpener that can collect dust and debris generated during knife sharpening.

SUMMARY

The present invention satisfies these needs. In one aspect of the invention, a knife sharpener allows for improved knife sharpening.

In another aspect of the invention, a knife sharpener comprises a sanding belt that can easily and consistently grind both sides of the edge of a knife.

In another aspect of the invention, a knife sharpener comprises an angle guide that allows a user to precisely select and/or monitor the angle of sharpening over a wide range of angles.

In another aspect of the invention, a knife sharpener comprises a sanding belt and includes a manner of preventing deflection of the sanding belt during the sharpening process.

In another aspect of the invention, a knife sharpener comprises an electromagnet for collecting dust and debris that results from the sharpening process.

In another aspect of the invention, a knife sharpener comprises a housing containing a sanding belt and a driving system that engages the belt to cause it to move in a sharpening area where a knife can come into contact with the sanding belt; a first angle guide having a surface against which a first side of a knife can be positioned so the edge of the knife can be positioned in the sharpening area; a second angle guide having a surface against which a second side of the knife can be positioned so the edge of the knife can be positioning in the sharpening area; and an angle adjustment mechanism that can adjust the angle of the first angle guide and the second angle guide to change the angle of the surfaces relative to the sanding belt.

In another aspect of the invention, a knife sharpener comprises a housing containing a sanding belt and a driving system that engages the belt to cause it to move in a sharpening area where a knife can come into contact with the sanding belt; an angle guide having a surface against which a side of a knife can be positioned so the edge of the knife can be positioned in the sharpening area; an angle adjustment mechanism that can adjust the angle of the angle guide to change the angle of the surface relative to the sanding belt; and a sanding belt platform beneath the sanding belt in the sharpening area, the sanding belt platform including a surface that limits the amount of deflection of the sanding belt when the sanding belt is contacted by a knife.

In another aspect of the invention, a knife sharpener comprises a housing containing a sanding belt and a driving system that engages the belt to cause it to move in a sharpening area where a knife can come into contact with the sanding belt; an angle guide having a surface against which a side of a knife can be positioned so the edge of the knife can be positioned in the sharpening area; an angle adjustment mechanism that can adjust the angle of the angle guide to change the angle of the surface relative to the sanding belt; and a magnet below the sanding belt, wherein the magnet attracts dust and debris generated when the knife contacts the sanding belt.

DRAWINGS

These features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings which illustrate exemplary features of the invention. However, it is to be understood that each of the features can be used in the invention in general, not merely in the context of the particular drawings, and the invention includes any combination of these features, where:

FIG. 1 is a schematic perspective view of a knife sharpener of the invention;

FIG. 2A is a schematic perspective view of the knife sharpener of FIG. 1A in a different position;

FIG. 2B is a schematic perspective view of the knife sharpener of FIG. 1A in a different position;

FIG. 3A is a schematic partially-sectional side view of a portion of the interior of a knife sharpener according to a version of the invention;

FIG. 3B is a schematic partially-sectional side view of a portion of a knife sharpener according to a version of the invention;

FIG. 3C is a schematic side view of a protractor of the knife sharpener according to a version of the invention;

FIG. 4A is a schematic partially-section side view of a portion of the interior of another version of a knife sharpener according to the invention;

FIG. 4B is a schematic partially-section side view of a portion of the interior of another version of a knife sharpener according to the invention;

FIG. 5A is a schematic partially-section side view of a portion of the interior of another version of a knife sharpener according to the invention;

FIG. 5B is a side view of another version of a protractor of the knife sharpener of FIG. 5A;

FIG. 6A is a schematic partially-section side view of a portion of the interior of another version of a knife sharpener according to the invention; and

FIG. 6B a schematic partially-section side view of a more complete interior of the version of a knife sharpener of FIG. 6A.

DESCRIPTION

The present invention relates to a knife sharpener. Although the knife sharpener is illustrated and described in the context of being useful for sharpening knives, the present invention can be useful in other instances. Accordingly, the present invention is not intended to be limited to the examples and embodiments described herein.

FIG. 1 shows a knife sharpener 100 in accordance with one version of the invention. The knife sharpener 100 includes a housing 105 that houses a sanding belt 110 that travels in a loop within the housing 105 in a rotary fashion. The sanding belt 110 includes an exposed portion 115 where the sanding belt 110 exits the housing 100 and is exposed. Within the exposed portion 115 of the sanding belt 110 is a substantially flat sharpening area 120. The sanding belt 110 is composed of an abrasive material that is sufficiently coarse and hard to sharpen a knife or other object by grinding away a portion of the edge of the knife. By knife it is meant any tool or utensil that has an angled edge, the angle of which is to be adjusted, altered, and/or maintained. The knife may have a blade with a single or double bevel or other configuration. Examples of knives include a butcher knife, a cleaver, a chef's knife or other food preparation knife, a steak knife, a table knife, a butter or cheese knife, a serrated blade, shears, scissors, a pincer, a machine blade, a lawn mower blade, a trimmer blade, a scythe, tools such as an axe, a chisel, a tool bit, a tipped tool, a leather punch, other components for tools, and the like. By sharpening it is meant the process of grinding away a portion of the edge of a knife in order to change or maintain the angle of the edge of the knife. Sharpening can include the removal of the sides of the edge to make the angle small and thus make the knife edge sharper or can include the removal of a portion of the tip of the edge to make the knife edge less sharp. In one version, multiple replaceable sanding belts 110 each of different coarseness can be provided so as to best perform the desired sharpening of a particular knife. The knife sharpener 100 can also be used for polishing by replacing the sanding belt 110 with a polishing belt.

To sharpen a knife using the knife sharpener 100, the knife edge is brought into contact with the sanding belt 110 in the sharpening area 120 of the knife sharpener 100. As the sanding belt 110 rotates in its loop, different portions of the sanding belt 110 will enter into the sharpening area 120. When the edge of the knife contacts the sanding belt 110, a portion of the edge is ground by the sanding belt 110. The angle of the knife when it contacts the sanding belt 110 will determine the sharpness of the edge of the knife.

In one version of the knife sharpener 100, an angle guide 125 is provided for maintaining the knife at a desired angle relative to the sanding belt 110 in the sharpening area 120. The angle guide 125 has a substantially flat surface 130 on which the side of a knife can be positioned so the knife can be directed toward the sharpening area 120. When maintained in the position on the surface 130, the edge of the knife is maintained at a desired angle relative to the sanding belt 110 and the edge is ground to a desired sharpness. The angle guide 125 can also include a guard 135 for improved and/or safer sharpening. The guard 135 can extend substantially parallel to the surface 130 to create a slot 140 into which the knife can be inserted. In another version, the guard 135 can be positioned at a slight angle relative to the surface 130 to create a slightly tapered slot 140. In this tapered version, the surface 130 and the guard 135 can provide a clamping action on the knife. The guard 135 helps to maintain the knife at the desired angle. In addition, the guard 135 helps to prevent the knife from being kicked upwardly when it contacts the rotating sanding belt 110 thus helping to prevent injury to a user.

In one version, the angle guide 125 of the knife sharpener 100 can include an angle adjustment mechanism 145 that adjusts the angle of the angle guide 125 relative to the sanding belt 110 in the sharpening area 120. In the version shown, the angle adjustment mechanism 145 includes an angle adjustment knob 150 that can be turned to change the angle of the angle guide 125. As can be seen in FIG. 1 and FIGS. 2A and 2B, the angle adjustment mechanism 145 can adjust the angle of the angle guide 125 through a range of angles. The angle, a, of the angle guide 125 represents the angle between the angle guide 125 and the sanding belt and/or the horizontal plane. For example, in the version shown, the angle guide 125 can be positioned from about 90 degrees, as shown in FIG. 2A, to about zero degrees, as shown in FIG. 2B, and to any number of angles in between, one of which is shown in FIG. 1. For example, the angle, a, can extend in various versions at its upper limit up to at least 50 degrees, up to at least 60 degrees, up to at least 70 degrees, up to at least 80 degrees, or up to at least 90 degrees. The angle can extend at its lower limit in various versions to 15 degrees or less, or 10 degrees or less, or 5 degrees or less, or as little as 0 degrees. Thus, the of angle adjustments can range from any of the above lower limits to any of the above upper limits or can be smaller ranges. The angle, a, can be measured from any portion of the angle guide 125. For example, the angle, a, can be measured from the surface 130, from the guard 135, or from the center of the slot 140. In one particular version, the angle, a, is measured from the center of the slot 140. With this version, the angle, a, represents the angle to the leading edge of the knife to be sharpened.

The knife sharpener 100 can also have a second angle guide 155. The second angle guide 155 includes a substantially flat surface 160 that functions in similar manner as the surface 130 of the first angle guide 125. Similarly, the second angle guide 155 can also include a second angle guide guard 165 that creates a slot 170 with the second angle guide surface 160 as with the first angle guide 125. The second angle guide 155 can be positioned at an angle, b, relative to the sanding belt 110. The angle, b, can be any of the above-mentioned angles discussed in connection with angle, a, of the first angle guide 125. In one version, the second angle guide 155 can be positioned at an angle, b, that is the same as but opposite to the angle of the first angle guide 125. As can be seen in FIG. 1, the angle, a, of the first angle guide 125 relative to the sanding belt 110 in the sharpening area 120 is the same as the angle, b, of the second angle guide 155 relative to the sanding belt 110 in the sharpening area 120. The angle adjustment mechanism 145 can be configured to simultaneously adjust both the first angle guide 125 and the second angle guide 155 and to maintain them at equal but opposite angles where angle a substantially equals angle b. Alternatively, the angles of the two angle guides can be separately adjustable and can be set to the same or different angles.

In use, the knife sharpener 100 can be used to sharpen one or both side of the edge of a knife blade. In its simplest use, the angle guide 125 can be positioned at a desired angle, and a knife can be inserted into the slot 140. As the sanding belt 110 rotates through the sharpening area 120, it will grind one side of the edge of the knife blade. In one version, the sanding belt 110 can rotate so that it moves towards the edge of the knife, i.e. from left to right in FIG. 1A. In another version, the sanding belt 110 can rotate so that it moves away from the edge of the knife, i.e. from right to left in FIG. 1A. In another version, the direction of rotation of the sanding belt 110 can be adjustable so that it can rotate towards the knife edge and can be switched to rotate away from the knife edge.

The knife sharpener 100 can also be used to grind the other side of the edge of the knife. This can be accomplished in a number of manners. When a single angle guide 125 is used, the knife can be removed from the slot 140 after the first side of the edge is ground and then flipped over and reinserted from the backside of the housing 105 to grind the other side of the edge. When the second angle guide 155 is provided, both sides of the edge of the knife can be ground from the same side of the housing 105. In this version, after the knife is ground in the first angle guide 125, the knife is removed from the slot 140 and inserted into the slot 170 in the second angle guide 155 so that the second side of the knife edge contacts the sanding belt 110. In this method the sanding belt can either continue to rotate in the same direction for both grinds or can be switched to rotate in the reverse direction for the second grind. When in the sanding belt 110 direction is reversed, both sides of the knife are ground by the sanding belt 110 moving towards the knife edge or both sides are ground by the sanding belt 110 moving away from the knife edge. This can produce a cleaner and more even knife edge.

A sanding belt 110 driving system 200 for use with one version of a knife sharpener 100 of the invention is shown in FIG. 3A. FIG. 3A is a schematic side view showing parts of the inside of the housing 105 of the knife sharpener 100. In this version, the sanding belt 110 is a continuous loop of material that is held under tension be being wrapped around a first wheel 205 and a second wheel 210. The first wheel 205 is also engaged by a drive belt 215 that is driven by a motor 220. When the motor 220 is activated, the motor 220 causes the drive belt 215 to rotate which then causes the wheel 205 to rotate. The wheel 205 engages the sanding belt 110 with sufficient friction and the sanding belt 110 is under sufficient tension that the rotation of the wheel 205 causes the sanding belt 110 to travel along its looped path. The second wheel 210 in this version is free spinning. The sanding belt 110 is caused to move across the sharpening area 120. In one version, the motor 220 is unidirectional. In another version, the motor 220 is bidirectional so the sanding belt 110 can either rotate clockwise or counterclockwise within the housing 105. In another version, the motor 220 can have variable speeds so the speed of the sanding belt 110 can be controlled. A knob on the front of the housing 105 can provide the directional and/or speed settings. In one particular version, the motor 220 is from about 100 to about 200 Watts and works on AC current and has adjustable speed (rpm) and direction. Alternatively, the motor 220 can be powered in any other manner, such as by DC through the use of one or more batteries, including a lithium-ion battery pack and the like. The motor 220 preferably has a protective casing that protects it from debris from the sharpening process.

The sanding belt 110 can also be removable and replaceable. As can be seen in FIG. 3A, one of the wheels, such as a second wheel 210, can be connected to the drive system by a moveable arm 225. The moveable arm 225 can be locked in the operating position where the second wheel 210 is in a first position 230 where the sanding belt 110 is under tension. The moveable arm 225 can also be selectively released from the operating position 230 and the wheel 210 can be moved to a second position 235 as shown by arrows 240. In the second position 235, the sanding belt 110 is no longer under tension and can be easily removed from the first wheel 205 and the second wheel 210 by sliding it off. The sanding belt 110 can then be cleaned and reinstalled, or a new sanding belt 110 can then be replaced and the second wheel 210 can be returned the first or operating position 230 so the new sanding belt 110 may be moved through the sharpening area 120. The new sanding belt 110 may be a sanding belt with the same characteristics as the old one or can be of a different coarseness, hardness, or the like. The sanding belt 110 may be made of leather, polyester cloth backing, or other similar material, with a coating of silicon carbide and aluminum oxide, diamond, wool, and/or the like depending on the application. For most sharpening purposes, the sanding belt 110 will have a silicon carbide and aluminum oxide coating having an American Standard grit from about 100 to about 100,000. In one version, multiple sanding belts 110 are provided, each having one grit of about one of the following: 100; 200; 300; 400; 600; 1000; 2000; 6000; 10,000; 14,000; 50,000; and 100,000.

As also shown in FIG. 3A, the knife sharpener 100 according to one version of the invention, includes a sanding belt platform 245. The sanding belt platform 245 has a top surface 250 over which the sanding belt 110 slides in the sharpening area 120. The sanding belt platform 245 is a stable platform that substantially prevents the sanding belt 110 from being deflected downwardly when the sanding belt 110 is contacted by a knife during the sharpening process. This allows the angle of the edge of the knife to be more accurate and consistent. If the sanding belt 110 were allowed to deflect, the angle of the knife relative to the sanding belt 110 would change depending on the amount of downward pressure being applied. Accordingly, an angle different than the desired angle would be ground into the edge. Also, the angle on one side of the edge might be different than the angle on the other side of the edge if different downward pressures are applied by the user. The sanding belt platform 145 can extent to either side of the sanding belt 110 by about 2 cm so that the knife being sharpened doesn't fall off the edge after moving off the belt and receive a blunted tip.

FIG. 3B shows details of a version of an angle adjustment mechanism 145 of the knife sharpener according to a version of the invention. In this version, an adjustment knob 150 can be grasped and turned by a user. The adjustment knob 150 controls a pulley system 255 that adjusts the angle, a, of the first angle guide 125 and the angle, b, of the second angle guide 155 simultaneously. A first pivot 260 is connected to the surface 130 of the first angle guide 125 in such a way that rotation of the first pivot 260 causes the surface 130 to rotate and changes its angle, a. Similarly, a second pivot 265 is connected to the surface 160 of the second angle guide 155 to cause a change of the angle b of the second angle guide 155. A cable 270 extends around at least a portion of the adjustment knob 150, the first pivot 260, and the second pivot 265, as shown, with the cable 270 being wrapped around the first pivot 260 and the second pivot 265 in opposite directions. Thus, rotation of the adjustment knob 150 causes the first pivot 260 and the second pivot 265 to rotate an equal but opposite amount. This results in movement of the surfaces 130,160 an equal but opposite amount, as shown by arrows 275, 280, respectively. The first angle guide 125 and the second angle guide 155 can be locked in place at the desired location. The locking mechanism can be a tightened knob that tightens in a bolt fashion.

A version of the knife sharpener 100 can include a digital protractor 285 or angle monitor as shown in FIG. 3C. The digital protractor 285 can be provided to measure the angle, a, between the first angle guide 125 and the sanding belt 110. In one version, the digital protractor 285 will measure the angle, a, between the midpoint of the slot 140 between the surface 130 and the guard 135 and the sanding belt 110. This ensures the angle of the grind is measured from the center 290 of a blade 295 rather than the outer side. When the slot 140 is tapered, as shown, the surface 130 and the guard 135 can more securely hold the center of the knife edge at the center of the slot 140. This can be accomplished by measuring or knowing the angle between the surface 130 and the guard 135. In one version, the digital protractor 285 can comprise a gear system, which would operate by the protractor being attached to a smaller gear piece that would move half the amount the guard 135 moves. Alternatively, a pulley configuration can be used. In another version, the protractor angle can be manually changed so as to measure from a different point on the blade and to get the desired cut to the leading edge based on this reference point.

FIG. 4A shows another version of a driving system 200 for the knife sharpener 100. In this version the first wheel 205 is made up of a wheel 305 that rotates about an axle 315 and the second wheel is made up of a wheel 310 that rotates about another axle 320. The wheel 305 of the first wheel 205 has an outwardly extending circular portion 325 that receives the drive belt 215. Rotation of the drive belt 215 by the motor 220 rotates the outwardly extending circular portion 325 which in turn rotates the wheel 305 and drives the sanding belt 110.

FIG. 4B shows the driving system of FIG. 4A and also shows another version of the moveable arm 225. In this version the moveable arm 225 includes a rigid arm 330 connected to a non-moveable plate 335 by a spring mechanism 340. The spring mechanism 340 biases the rigid arm 330 away from the plate 335. The rigid arm 330 is connected to the axle 320 of the wheel 310. When the spring mechanism 340 is uncompressed, the second wheel 210 is in the first position 230. When the spring mechanism 340 is compressed, for example by hand, the second wheel 210 can be moved to the second position 235 so the belt can be removed.

FIGS. 5A and 5B show an alternative version 400 of the angle adjustment mechanism 145. In this version, the angle adjustment mechanism 145 includes a first circular plate 405 and a second circular plate 410. The first circular plate 405 has teeth 415 that engage teeth 420 on the second circular plate 410. The first circular plate 405 is rigidly attached to the angle guide 125 so that rotation of the first circular plate 405 changes the angle a of the angle guide 125. The second circular plate 210 is rigidly attached to the second angle guide 155 (not shown in FIG. 5B for clarity). By the interaction of the teeth 415 of the first circular plate 405 and the teeth 420 of the second circular plate 410, rotation of the first circular plate 405 causes an equal but opposite rotation of the second circular plate 410. By this action, the angle, a, of the first angle guide 125 and the angle, b, of the second angle guide 155 are equal.

The rotation of the first circular plate 405 and the corresponding rotation of the second circular plate 410 can be performed manually, such as by a rotatable knob, or can be performed automatically. FIG. 5A shows an electronic angle adjustment system 425. The electronic adjustment system 425 includes a rotary encoder 430 or other electronic dial system that is connected to a circuit board 435 where different devices can be programmed and connected. The rotary encoder 430 may also be connected to a digital display 440 that displays the current angle of the angle guide. The components are connected to a source of power. In one version, the power source can be part of the rotary encoder/dial setup. In another version, the components can be powered by a separate motor, such as motor 220.

One or more magnets, such as one or more electromagnets, may be provided within the housing 105 of the knife sharpener 100. The electromagnet may be positioned near the sharpening area 120 so that the electromagnet attracts debris 450 that is ground off the knife during the sharpening process. After sharpening, the electromagnet can be turned off, so the debris can be removed.

FIG. 6A shows a version of a knife sharpener 100 where a magnet 455, such as an electromagnet, is positioned near the bottom of the housing 105. A cable 460 can provide power to the electromagnet, for example from the motor 220. The metal debris 450 is drawn toward the magnet 455 as shown by arrows 465. FIG. 6B shows a version of the knife sharpener 100 with all of the above features operating together. An internal debris director 470 can be provided to funnel dust and debris toward the magnet 455. A director can also or alternatively be attached to one or more of the angle guides.

The housing 105 may have a top portion that is pivotally attached to a bottom portion so that access to the interior of the housing can be obtained. This allows for the changing of sanding belt 110, cleaning, repair, and the like. In another version, the top portion can be liftable from the bottom portion to provide the access.

The housing 105 and the knife sharpener 100 can be any suitable size. For example, the width of the housing may be from about 5 cm to about 50 cm, or from about 15 cm to about 30 cm. The width of the sanding belt can be from about 3 cm to about 13 cm, and in one version is about 8 cm.

In another version of the use of the knife sharpener 100, the underside of the angle guide 125 can be used as a guide for the knife to be sharpened. This is particularly useful for sharpening chisels. The back of the knife can be placed against the underside of the angle guide 125. The user would then push the knife towards the sanding belt 110 to cut the desired angle into the blade.

In another version of the knife sharpener 100, the sanding belt 110 can be replaced by a different type of moving coarse surface. For example, the course surface may oscillate or vibrate back and forth from front to back or from side to side.

Although the present invention has been described in considerable detail with regard to certain preferred versions thereof, other versions are possible, and alterations, permutations and equivalents of the version shown will become apparent to those skilled in the art upon a reading of the specification and study of the drawings. For example, the cooperating components may be reversed or provided in additional or fewer number. Also, the various features of the versions herein can be combined in various ways to provide additional versions of the present invention. Furthermore, certain terminology has been used for the purposes of descriptive clarity, and not to limit the present invention. Throughout this specification and any claims appended hereto, unless the context makes it clear otherwise, the term “comprise” and its variations such as “comprises” and “comprising” should be understood to imply the inclusion of a stated element, limitation, or step but not the exclusion of any other elements, limitations, or steps. Therefore, any appended claims should not be limited to the description of the preferred versions contained herein and should include all such alterations, permutations, and equivalents as fall within the true spirit and scope of the present invention. 

What is claimed is:
 1. A knife sharpener comprising: a housing containing a sanding belt and a driving system that engages the belt to cause it to move in a sharpening area where a knife can come into contact with the sanding belt; a first angle guide having a surface against which a first side of a knife can be positioned so the edge of the knife can be positioned in the sharpening area; a second angle guide having a surface against which a second side of the knife can be positioned so the edge of the knife can be positioning in the sharpening area; and an angle adjustment mechanism that can adjust the angle of the first angle guide and the second angle guide to change the angle of the first angle guide and the second angle guide relative to the sanding belt.
 2. A knife sharpener according to claim 1 wherein the angle adjustment mechanism simultaneously adjusts the first angle guide and the second angle guide so that the angles are equal but opposite.
 3. A knife sharpener according to claim 2 wherein the angle adjustment mechanism comprises a knob connected to a pulley system.
 4. A knife sharpener according to claim 2 wherein the angle adjustment mechanism comprises a first plate connected to the first angle guide and a second plate connected to the second angle guide, each plate including teeth that engage with one another.
 5. A knife sharpener according to claim 2 wherein the angle adjustment mechanism comprises an electronic adjustment system with a rotary encoder.
 6. A knife sharpener according to claim 1 wherein the knife sharpener includes a display that displays the angle of the first angle guide relative to the sanding belt.
 7. A knife sharpener according to claim 1 wherein the first angle guide includes a guard that together with the surface of the first angle guide defines a slot into which the knife may be inserted.
 8. A knife sharpener according to claim 1 wherein the angle of the first angle guide can be adjusted so the angle of the leading edge of the knife relative to the sanding belt can range from about 5 degrees or less to about 80 degrees or more.
 9. A knife sharpener according to claim 1 wherein the angle of the first angle guide can be adjusted so the angle of the leading edge of the knife to the sanding belt can range from about 0 degrees to about 90 degrees.
 10. A knife sharpener according to claim 1 wherein the sanding belt is in the form of a loop.
 11. A knife sharpener according to claim 1 wherein the driving system can drive the sanding belt is more than one direction.
 12. A knife sharpener according to claim 1 wherein the driving system can drive the sanding belt at variable speeds.
 13. A knife sharpener according to claim 1 wherein the housing includes a sanding belt platform on the side of the sanding belt opposite the side that can contact the knife in the sharpening area, the sanding belt platform including a surface that limits the amount of deflection of the sanding belt when the sanding belt is contacted by a knife.
 14. A knife sharpener according to claim 1 wherein the housing includes a magnet below the sanding belt, wherein the magnet attracts dust and debris generated when the knife contacts the sanding belt.
 15. A knife sharpener comprising: a housing containing a sanding belt and a driving system that engages the belt to cause it to move in a sharpening area where a knife can come into contact with the sanding belt; an angle guide having a surface against which a side of a knife can be positioned so the edge of the knife can be positioned in the sharpening area; an angle adjustment mechanism that can adjust the angle of the angle guide to change the angle of the angle guide relative to the sanding belt; and a sanding belt platform on the side of the sanding belt opposite the side that can contact the knife in the sharpening area, the sanding belt platform including a surface that limits the amount of deflection of the sanding belt when the sanding belt is contacted by a knife.
 16. A knife sharpener according to claim 15 wherein the angle adjustment mechanism comprises an electronic adjustment system with a rotary encoder.
 17. A knife sharpener according to claim 15 wherein the knife sharpener includes a display that displays the angle of the angle guide relative to the sanding belt.
 18. A knife sharpener according to claim 15 wherein the first angle guide includes a guard that together with the surface of the angle guide defines a slot into which the knife may be inserted, and wherein the angle of the angle guide is measured from the midpoint of the slot.
 19. A knife sharpener comprising: a housing containing a sanding belt and a driving system that engages the belt to cause it to move in a sharpening area where a knife can come into contact with the sanding belt; an angle guide having a surface against which a side of a knife can be positioned so the edge of the knife can be positioned in the sharpening area; an angle adjustment mechanism that can adjust the angle of the angle guide to change the angle of the angle guide relative to the sanding belt; and a magnet below the sanding belt, wherein the magnet attracts dust and debris generated when the knife contacts the sanding belt.
 20. A knife sharpener according to claim 19 wherein the magnet is an electromagnet. 